An ever-increasing number of portable devices, such as mobile telephones, portable media players and portable computers, for example, are now available to consumers. Accordingly, as a device becomes portable, the usage conditions that it is subjected to will vary greatly, such as from a device under static use such as a desktop computer, for example. Portable devices are more likely to experience shocks from impacts and varying thermal operating conditions arising from the different environments in which they may be used. In realization of this, the microelectronics industry has adopted standards to gauge how well the various microelectronic components, such as printed circuit boards (PCB) and their mounted components, fair under such conditions.
An example of said standards is the JEDEC standard (JESD22-B111) which is capable of qualifying the component-board interconnection under impact testing. However, the JEDEC test requires the assembling of the component onto a PCB, a process that is not cost effective when done solely for testing purposes. With respect to testing, the present industry practice of solder ball shearing using a standard ball shear tester is not desirable for at least two reasons. Firstly, the ball shear tester is unable to effectively induce the desired mode of failure testing due to its low shear speed. Secondly, the minute specimen of the solder ball represents a challenge, as its size and geometry prevent accurate characterization of the failure when using standard impact testers such as the Charpy or Izod testers as they lack adequate testing resolution.
In the case of PCB components, Siviour et al. [Dynamic Properties of Solders and Solder Joints, J. Phys. IV France 110(2003)] describes an experiment using an Instron loading machine to study the effect of varying strain rates upon the solder joints of PCBs. The solder joint, consisting of a solder ball, is attached to a copper pad on a polymer substrate. In the study, a brass blade struck the solder ball at a given speed and the load required to shear the solder ball was recorded. However, the shear speed peaked at slightly over 1 m/s, meaning that the range of the shear speed achieved in this study was rather limited.
More recently, Date et al. [Impact Reliability of Solder Joints, 2004 Electronic Components and Technology Conference, 2004], describes a mechanical testing apparatus for solder joints. The mechanical test was carried out using a pendulum impact test in which the pendulum setup allowed the test shear rate to range between 0.1 mm/s-1.4 m/s. The fracture energy of the solder joint was taken to equal to the decrease in kinetic energy of the pendulum after it had struck the solder joint. However, a drawback of the method described by Date et al. is that only the fracture energy is provided and no information on the fracture strength is measured. Furthermore, the accuracy of attributing the (expected) loss of kinetic energy of the pendulum to the fracture energy of the solder joint is questionable, as the change in kinetic energy may have resulted from other losses, such as losses due to the vibration of the pendulum as well as to heat and sound in addition to the energy dissipated upon impacting the solder joint.
Despite the above-mentioned developments, there remains a need for a microelectronics interconnection impact tester that is capable of producing the desired failure testing mode in order to provide quantitative and accurate measurements not only regarding the fracture energy, but also regarding the fracture strength of microelectronics interconnections. It is also desirable to provide an impact tester through which, easily reproducible results on test specimens of minute size and geometry are achievable. Furthermore, it is also desirable to provide a cost-effective tester that is also commercially viable for the microelectronics industry to adopt on a large scale.
In order to solve the above-mentioned problems and fulfill the mentioned needs, an impact tester having the features according to the independent claims is provided according to the present invention.